The invention relates generally to multichannel heat exchangers with dissimilar tube spacing.
Heat exchangers are used in heating, ventilation, air conditioning, and refrigeration (HVAC&R) systems. Multichannel heat exchangers generally include multichannel tubes for flowing refrigerant through the heat exchanger. Each multichannel tube may contain several individual flow channels. Fins are positioned between the tubes to facilitate heat transfer between refrigerant contained within the tube flow channels and external air passing over the tubes. Multichannel heat exchangers may be used in small tonnage systems, such as residential systems, or in large tonnage systems, such as industrial chiller systems.
In general, heat exchangers transfer heat by circulating a refrigerant through a cycle of evaporation and condensation. In many systems, the refrigerant changes phases while flowing through heat exchangers in which evaporation and condensation occur. For example, the refrigerant may enter an evaporator heat exchanger as a liquid and exit as a vapor. In another example the refrigerant may enter a condenser heat exchanger as a vapor and exit as a liquid. These phase changes result in both liquid and vapor refrigerant flowing through the heat exchanger flow channels. In particular, one portion of the heat exchanger may contain vapor refrigerant undergoing de-superheating while another portion of the heat exchanger contains a liquid undergoing subcooling.
The phase of the refrigerant may impact the efficiency of the heat exchanger because different phases of refrigerant possess different heat transfer properties. For example, vapor phase refrigerant may pass through the flow channels at a higher velocity than liquid phase refrigerant, resulting in less heat transfer occurring for the tubes containing the vapor phase refrigerant. In another example, employing a heat exchanger functioning as a condenser, the vapor refrigerant may need to give off both latent and sensible heat to become a liquid refrigerant while the liquid refrigerant may need to give off only sensible heat to undergo subcooling.